Starting yesterday AA increased seat supply 40% in its GRU-MIA operations. As customary in previous years, the seat supply increased because of one additional daily flight AA2943/AA2944 (daylight flights) and replacement of B763 with the B777 (15F/35C194Y) for flights AA930/907.

Just to note though, what they are doing this year is not customary. While they have typically increased MIA-GRU to 4x daily during December and January (AA would do it all winter if Brazil would them), this year, for the first time, they will have three daily 772 flights on MIA-GRU, rather than just one.

Also, the daylight flight is now year-round. The seasonal flight is now a redeye. AA doesn't have the equipment to run three daily redeyes, especially with new routes like ORD-DME, JFK-MXP, etc.

And the US is trying to negotiate much greater access for US carriers to Brazil, including cities outside of GRU and GIG. At the same time, JJ and RG are aggressively adding international capacity and DL is flying its 764s to Brazil for the first time as well as operating daylight flights where they can (although it appears they have to move their overnight flight later on the days the daylight flight operates - supposedly they had to do that in order for the Brazilian government to give them the right to operate the daylight flights).
Given the growth in the market, AA would be foolish not to take every opportunity it can.